In this research the impact of board governance orientation and board processes on board role performance and board effectiveness is examined. Building on existing literature, a model that relates board governance orientation (agency, stakeholder, stewardship and resource dependency) and board processes (cohesiveness, cognitive conflict, affective conflict, communication quality, effort norms, trust and the use of knowledge & skills) to board effectiveness via three mediating variables, board control role, board service role, and board strategy role is developed. The model was tested through a survey of listed companies in the UK. The results are based on 74 companies. The findings show (a) the board undertakes two distinct roles, control and service; (b) process variables, most notably cognitive conflict and the use of knowledge & skills, significantly influence board effectiveness mediated by the board’s control and/or service role; (c) structural variables, specifically the proportion of outsiders on the board, impacts on the board control role; (d) understanding board effectiveness requires a multitheoretic perspective.